1. Field of the Invention
This invention relates to the general field of dynamic storage of pallet-type loads, for instance; it relates more particularly to a safety system for the load separation devices in dynamic storage chutes.
2. Discussion of Background
The dynamic storage facilities are made up of chutes fitted with rollers or cylinders mounted parallel to one another on beams forming a frame which is tilted from its upstream to its downstream section. These rollers and/or cylinders determine a raceway on which the loads, generally handling pallets, are placed.
In order to suppress the problems associated with the extraction of the loads located at the lower portion of the storage chute, and notably that of the pressure exerted onto the end load by the accumulation of the upstream loads, a load separation device is commonly used at the level of the downstream end of the chute. This device is suited to isolate at least the first load, located downstream on the facility, with respect to the other loads which are waiting, upstream, in order to allow smooth extraction of this first load, without causing any problems, using for instance a fork-lift.
These separation devices are constituted of a pedal and of a stop, interconnected by a pole- or a tie-shaped linking rod. The pedal has been accommodated at the end of the chute and is designed to be actuated by the downstream load; the stop is used to retain the upstream load(s) in order to separate them from the load located at the downstream end. This stop is brought into active retaining position by the pedal when the latter is actuated by the end downstream load and it is de-actuated when the said downstream load is removed, in order to let the following load take its place at the end of the chute and actuate, in turn, the pedal as well as the retaining stop for the other loads.
Moreover, to provide greater safety when handling the load removed downstream of the chute, it proves interesting to retain the upstream load(s), to give some time to the operator to remove the downstream load without being affected by the pressure of the other loads on the chute. In this view, the load separation devices are usually fitted with means enabling to prevent too soon a release of the stop when removing the downstream load.
The documents FR-2 639 331 and DE-GM 7 534 405 describe two separation devices. In both these facilities, the end pedal controls the retaining stop directly, via a tie rod or a pole. The retaining stop is rotatably mounted on an articulation axis and it is subject to balancing means round the said axis which tend, by themselves, to bring the pedal back into raised position and to put the said stop in inactive position. These balancing means enable handling the separation device with minimum encumbrance; the end pedal can be actuated by any type of load, even by very light loads.
The separator according to the document FR-2 639 33 1 follows a principle in which the control of the stop is delayed by a particular interconnection between the handling pedal and the pulling rod. In such a case, the beginning of the motion of the pedal, linked to the extraction of the end load, has little influence on the motion of the stop; when the pedal reaches the end of its stroke, its motion is transmitted integrally to the said stop, until the latter is de-actuated.
With this separation device, the retaining stop is automatically de-actuated as soon as there is no contact between the pedal and the end load any longer. In spite of the provisions adopted to delay this de-actuation, the construction features of these gearworks cause quite a rapid release of the stop.
In the document DE-GM 7 534 405, the arrival of a load at the end of the chute actuates the retaining stop located upstream, but also a system to lock the pedal in lower position. The end load can be removed and handled without modifying the position of the separation device and hence without de-actuating the retaining stop. This de-actuation is carried out by a positive manoeuvre, manually or otherwise, on the locking means mentioned previously, when the operator wishes to move a load forward.
Other types of installations, operating according to different principles, are also known.
The document GB-1 009 128 describes a dynamic storage chute for pallets, fitted with a load separation device, consisting of an end pedal controlling a retaining stop via a pulling rod. This rod comprises two spaced shoulders serving, the former, to actuate the retaining stop via a toggle joint which, moreover, locks the said stop in active position and the latter, to de-actuate the said retaining stop. The second shoulder is suited to control the retaining stop just when the end pedal comes away from the pedal. This feature enables to delay the release of the loads stored upstream; the operator has therefore slightly more time to handle the load being picked-up.
As for the purposes of the document FR-2 639 331, the retaining stop is automatically de-actuated as soon as contact is lost between the end load and the pedal, which causes quite a fast release of the stop. On the other hand, a toggle joint is interposed between the end pedal and the retaining stop; unlocking the said toggle joint calls for a sizeable energy, which is provided by a spring-loaded accumulator. The energy in question is derived by the accumulator from the loads in motion, which actuate the end pedal, which limits the multi-purpose nature of the installation in terms of load weights. Indeed, according to their speeds and to their weights, the smaller loads may not possess sufficient kinetic energy to lower the end pedal combined to an energy accumulator.
This safety device is not optimum whatever the load conveyed and hence, it is not universally applicable.
The document U.S. Pat. No. 5,213,189 presents a load separation device constituted, as in the patent GB-1 009 128, of a pedal connected to the retaining stop by a rod associated with a locking toggle joint. The pedal is located at the downstream end of the chute and it is interconnected to a delay member which controls the release of the stop.
The delay member is constituted of a leak controlled-type jack, whose rod is interconnected to the end pedal. When the pedal is actuated by a load, causing the retaining stop to adopt an active position and the toggle joint to be locked, the said pedal compresses a spring-loaded accumulator and brings the jack's plunger back into a position corresponding, emblematically depicted, to the resetting of a delay member.
When the operator removes the load at the downstream end of the chute, the pedal rises slowly, regardless of the manoeuvring of the downstream load, but in relation to the leak of the delay jack, i.e. in relation to the motion of the jack's plunger.
On reaching a time-out pre-set in relation to the jack's leak rate, the rod connecting the pedal to the stop releases the toggle joint, which causes the loads retained by the said stop to be released, enabling the former to move forward on the chute. The first of these loads will now stand on the pedal in order, again, to raise the retaining stop which normally confines the upstream loads. The loads moving on the chute are conveyed, in the lower section of the chute, at different speeds to allow this separation to take place. The speed-controlled load separation means are not part of this invention.
In this embodiment, the energy necessary to unlocking the toggle joint is derived from the kinetic energy of the mobile loads reaching the end of the chute. In the case of loads with smaller weights, the kinetic energy may prove insufficient to actuate the pedal, raise the retaining stop and switch the spring(s) forming the accumulator system on; there again, the separation device in question is not universally applicable.